1. Field of the Invention
The present invention relates to an electronic device comprising heat radiation members arranged on two levels for radiating heat generated by a circuit part.
2. Description of the Related Art
A semiconductor circuit part generates heat in use, and a heat radiation member called a heat sink is attached to the circuit part to cool it. Also, the circuit part with the heat radiation member attached thereto is cooled by cooling air. Among circuit parts, an MPU is an especially important part and generates much heat and, therefore, requires sufficient cooling.
A circuit part with a heat radiation member attached thereto operates smoothly under a predetermined operating condition, but may not operate so well under a more difficult operating condition. For example, a circuit part with a heat radiation member attached thereto, which is designated to be used in an environment of 50.degree. C., operates smoothly under the designated condition but sometimes fails to operate smoothly in an environment of 70 to 80.degree. C.
In a different operating condition, therefore, it is necessary to use a heat radiation member of a different heat radiation characteristic. In a circuit part with a specific heat radiation member fixed thereto, however, it is not easy to remove the heat radiation member from the circuit part and attach another heat radiation member to the circuit part, and such a mounting/demounting work often results in a higher cost. Therefore, it is sometimes better to improve the heat radiation characteristic of the circuit part while the originally attached heat radiation member is kept on the circuit part.